Torsional pendulum drive



Nov. 3, 1931. H. L. SARGENT TORSIONAL PENDULUM DRIVE Filed Dec. 6, 12530lulllHHlllll llllllllllh Inventor Herbert L. Sargent, y M

His Attorneu.

Patented Nov. 3, 1931 PATENT OFFICE HERBERT L. SARGEN T, OF SALEM,MASSACHUSETTS TORSIONAL PENDULUM DRIVE Application filed December 6,1930.

believed to be novel and patentable will be pointed out in the claimsappended hereto. For a better understanding of the invention referenceis made in the following description to the accompanying drawings which20 show in Fig. 1 a general view of the invention as ap lied to theoperation of a torsional pendiilum advertising device. Fig. 2 shows aperspective detail View of the driving mechanism between the motor andpendulum; and Figs. 3 and 4 show detail views of a portion of thismechanism in different operating positions.

The advertising device represented in Fig. 1 comprises a'platform 10upon which various commodities m y be Placed for display purposes. Theplatform is supported by suspension members 11 from the lower end of aflatsteel strip 12 the upper end of which is fastened to a stationarysupport 13. It will be evident that if the platform is given a turn inone direction the parts will oscillate as a torsional pendulum due tothe torsional spring action of the flat steel portion 12. The characterof the oscillations will depend upon the length of part 12, the weighton the platform etc. However, such oscil- 'lations will. soon die outand the platform will come torest in a neutral position unless someexternal oscillation retaining force is applied thereto at the propertime and di- Serial No. 500,603.

rection. The force necessary to apply to maintain the pendulum inoperation at its natural oscillation period is small and is supplied inaccordance with my invention by a small electric motor operating on thependulum mechanism, a preferred form of which is shown in Fig.2.

Referring to Fig. 2 the stator of the electric motor is shown at 14.This motor may be most any type of self-starting rotary motor designedto be continuously energized without injury should it become stalled.

- I have obtained satisfactory operation using the type of motordescribed in United States Patent No. 1,283,435, October 29, 1918, toWarren. Such a motor is self-starting and may be continuously energizedwithout injury even when stalled. It consumes small current and when itsspeed is reduced by gears furnishes enough power for the purpose inquestion. In Fig. 2, 15 represents a casing containing reduction gearsbetween the motor and a crank arm 16 which is driven from the motor at aslow speed in a clockwise direction. At the outer end of this crank armis a member 17 pivoted to the arm at 18. Member 17 is secured to a rod19 which is pressed through 17 at right angles to the plane of rotationof arm 16. Rotation of the pivoted member 17 about pivot 18 is limitedin one direction by the stop pin 20 and is normally restrained frommovement in the other direction by a spring 21 fastened between the rearextension of rod 19 and the hub of crank arm 16. The torsional spring 12is hung from the common support 13 a few inches above and in front ofthe crank arm 16 and extends downward in alinement with the axis ofrotation of the crank arm. An arm 22-is fastened to the'torsional member12 a few inches below the axis of crank arm 16 much nearer the upperthan the lower end of member 12. Arm 22 is at right angles to thetorsional member and when the latter is in a natural position arm 22extends toward crank 16. Near the outer end of arm 22 is secured anupwardly extending rod 23 and a block 24 in which both rods 23 and 19may slide, fastening these rods together in driving relation. Thus block24 may slide horizontally on rod 19 and vertically on rod 23. Thisswivel arrangement converts the rotary movement of crank 16 into anoscillatory movement of arm 22 in planes at right angles to each other.The oscillatory movement of arm 22 is thus conveyed to the torsionalpendulum spring 12 for the purpose of supplying sufficient energyto'keep the torsional pendulum in operation after it is started. Ifcrank 16 and arm 22 revolved continuously at the same uniform, speedtheir component movements in the same horizontal directtion would varyaccording to a sine law. While the crank arm 16 tends to revolve at auniform speed it is ofcourse impossible for arm 22to do so or to have ahorizontal comvponent movement parallel to arm 16 which varies asa sinelaw. This is because arm 22 must slowdown, stop and reverse itsdirection at the extremity of each oscillation.

In order to transfer beneficial horizontal motion from one partto theother forthe purpose in question it is therefore necessary to ,bringtheir laws of movement in thecoinmon direction into coincidence or inphase, so to speak, or else provide a flexible tie between the partsthat will permit relative horizontal ,movementinjthesame direction. Thisis accomplished in part by allowing a variation in speed (including zerospeed) of motor-14c and in part byflthe flexible connection affordedbythe pivoting of member 17 on arm 16. The flexible connection betweenrod 19 d arm ,16 by reason of having part 17 pivoted atl8 is made use ofat the extremitiesof the oscillation of the torsional pendu- .lum tostall the driving motor momentarily while the torsional pendulum isreversing. Energyis absorbed ,by spring 21 in bringing the torsionalpendulum to a stop and is given out again in starting the torsionalpendulum in .the reverse direction. Thus the torsional pendulum isreversed quicker than would otherwise'be the case and?v more livelymovement of the advertising display is obtained.

To accomplish these results pins '25 are provided on-opposite diametersof the path of movement of arm 16, which pins extend .into the path ofmovement of the outer 'fhooked endof the hinged member 17. As arm 16rotates opposite these pins 25 the hookin member 17 engages-the pinsnear the extremity of the swing of the torsional pendulum. The motor 14is stalled while the momentum of the torsional pendulum carries arms 23and 24 outward sufliciently to tu'rn'member ,17 .on its pivot againstthe tension ofspring 21 as represented in Fig. 3.Theiparts,areadjustedso that the hook memiher is releasedjby 'pin 25just before or as the torsional pendulum reaches its extreme movementand stops. The motor 14 in the meantime has moved arm 16 slowly to theextent permitted by the unhooking action just described. The position ofthe parts at this stage is substantially as represented in Fig. 4.Spring 21 now slowly pulls the hook 17 back into the position shown inFig. 2 against stop 20 accelerating the torsional pendulum in its newdirection of movement. This stalling and slow movement of the motor atthe extremities of the swing of torsional pendulum and the speeding upof thereversing of the torsional pendulum corrects the phase relationbetween the two parts or allows the torsionalpendulumto catch up inphase, so to speak, with crank arm 16. As the hook 17 comes back-intothe position shown in Fig. 2 and the torsional pendulum increases inspeed the speed of motor 14 increases and supplies energyto acceleratethe pendulum, the parts now moving together through the swivel block 24,said block moving downward on rod23 and toward 16 on arm 19 as the arm19 moves through the first quadrant of the lower-portion of its swing.The parts thus move in phase until the opposite extremity ot'thependulum swing is reached, where the same operation is repeated as hook17 engages the left hand pin 25 with the arm 16 moving in an upwarddirection. Thus each revolution of crank 16 corresponds to a completeoscillation of the pendulum, and alternate half revolutions of arm 16corresponds to consecutive movements of the pendulum inoppositedirections. 1

As represented in Fig. 2 the angle of swing of the torsionalpendulum atthe point. where arm22 is attached is slightly less than 180 degrees.The platform 10 however may turn through a much larger angle dependingupon the length of member 12 below arm 22, the

7 weight of'platform' 10, etc. andthese factors will determine thereversal period and the lengthfof time the motor is stalled.

The .energy necessary to keep a torsional pendulum in operation is verysmall. I have found that a motor having an input of less than 1/100000horse-power will maintain a pendulum having a platform weight of 100pounds in constant oscillation in the manner apparatus establishes adefinite phase relation between the motor and pendulum for shortintervals of time during the swing of the pendulum in either directionand adds suflicient energy thereto to overcome friction,

etc. and maintain the pendulum in oscillation and by the apparatusherein described. The I cated at 28 which supplies the electric motorlet. The lead may be extended to the table as indicated at 29 in orderto operate electrical devices, such as the electric clock represented at30, displayed on the oscillatory table.

Various dilierent arrangements for conveying motion from the electricmotor to the torsional pendulum will occur to those skilled in the artand I do not wish to be limited to the particular arrangement describedbut seek claims commensurate with the scope of the invention.

What I claim as new and desire to secure r' by Letters Patent of theUnited States, is

1. A torsional pendulum, a self-starting rotary motor, and motiontransmitting driving means connected between the motor and pendulum forimparting energy from the motor to the pendulum in both directions ofoscillation of the pendulum to maintain the pendulum in operation afterbeing started.

2. A torsional pendulum, a self-starting continuously energized, rotaryelectric motor, and motion transmitting driving means between said motorand pendulum for imparting energy from the motor to the pendulum in bothdirections of oscillation of the pendulum for maintaining the latter inoscillation after it is started.

3. A torsional pendulum, a self-starting rotary electrical motor, saidmotor being continuously energized and designed to withstand continuousenergization without injury when stalled, a motion transmitting drivingconnection between said motor and pendulum which permits the motor todrive the pendulum in both directions of its oscillatory movement andcauses the motor to be stalled at the extremities of the oscillation ofthe pendulum when its motion is reversing.

l. Atorsional pendulum, a rotary electric motor for maintaining saidpendulum in op eration after being started, said motor beingself-starting, continuously energized and capable of being stalledwithout injury, and means connected between the motor and pendulum fortransforming the rotary motion of said motor into the oscillatory motionof said pendulum, said means causing the stalling of said motor when themotion of the pendulum is reversing at the extremities of itsoscillation.

A torsional pendulum, a motor, a crank rotated in a vertical plane inone direction only by said motor, an arm extending horizontally fromsaid pendulum, a driving connection between said crank and arm wherebyrotary movement of the crank is converted into an oscillatory movementof said arm for maintaining said pendulum in operation after it isstarted, and lost motion means in said driving connection for stoppingthe crank arm each half revolution in substantially horizontal positionswhen the a crank havinga horizontal axis of rotation at right angles tothe axis of oscillation of the pendulum, and means connecting said crankand pendulum for causing a complete oscillation of said pendulum foreach revolution of said crank, the two horizontal positions of the armcorresponding to the extremities of oscillation of the pendulum, saidmotor and connection serving to maintain said pendulum in oscillationafter it is started.

7. A torsional pendulum, a rotary motor having a crank arm, with itsaxis of rotation horizontal and at right .angles to the axis ofoscillation of the pendulum, a member pivoted on a horizontal axis atthe outer end of the crank, a horizontal rod extending from said membertoward the pendulum, a horizontal arm extending from the pendulum towardthe crank, a vertical rod carried at the outer end of said arm, saidhorizontal and vertical rods being connected by a block sliduble on bothrods, said arrangement forming a driving connection between the motorand pendulum to maintain the latter in oscillation after it is started,the two horizontal positions of the crank corresponding to the twoextremities of the oscillation of the pen dulum, means for engaging thepivoted memher when the crank is in substantially horizontal positionsto stop the motor, said pivoted member then being turned on its pivot torelease the crank by the momentum of the pendulum as it approaches theextremities of its oscillations, and a spring resisting such turning ofthe pivoted member and serving to accelerate the pendulum in theopposite direction and restore the pivoted member to its originalposition after the crank has been released.

8. A torsional pendulum, a motor for supplying energy to maintain saidpendulum in oscillation after being started, a crank operated by saidmotor, a driving connection between said crank and pendulum wherebyalternate half revolutions of the crank corresponds to the successivemovements of the pendulum in opposite directions and each completerevolution of the crank corresponds to a complete oscillation of thependulum, said driving connection maintaining a definite phase relationbetween the movement of the crank and pendulum except when the pendulumis reversing at the extremities of its oscillations, and means formomentarily stopping the rotation of the crank as the pendulumapproaches the extremities of its oscillations.

9. A torsional pendulum comprising a long flat metallic suspensionmember secured at its upper end and supporting a weight at its lowerend, a self-starting rotary electric motor, a driving animation saidmotor and the suspensibh member fiheb'ed to the latter nt a point nearerits upper than its lower end for mnviting the rotary m0- tion of said moto'r ime an oscillatory motien of said endulum fbi supplying ,ihergy1'10 the pendulum f0! both directions "of it's mqve m'e'nt to maintainsaid nduhi'm 'ih oillati'on after bihgstart' In witness whereof, I havehereunto set my hand this fii'st day f December, 1930. HERBERT L.SARGENT.

